1. Field of the Invention
The present invention relates to an apparatus and method for quantitatively measuring influence on a product, such as a device or component, by temperature when some temperature stress is applied to the product in a process for manufacturing or using it.
2. Description of the Related Art
Recently in the semiconductor component field packages are getting larger due to a multi-pinned component and getting thinner due to a lighter, thinner miniature device on which a component is mounted. Especially in the case of a surface-mounted component a product package cannot resist thermal stress at the time of reflow and a thinner package is one factor in increased quality failures such as lower reliability and poor soldering.
FIG. 1A shows the conventional test method for checking the change of a surface mounted component at the time of reflow. Conventionally the change of the component is checked by visually inspecting a swelling, crack or distortion left on measured component 2, scanning them with supersonic waves and measuring their dimensions after some thermal stress is applied in a reflow furnace 1, because there is no technology for measuring the change of the component while heating or cooling it. In reflow furnace 1, a different temperature distribution can be set in different positions and a thermal change can be given to components moving in the furnace. For the dimension measurement instrument 3 instruments such as a micrometer and calipers are used.
However, there are the following shortcomings in the conventional test method:
In the conventional method the change of component 2 is checked after a thermal stress is applied. However, when component 2 is actually mounted on a printed circuit board using reflow furnace 1, it is considered that component 2 transitionally undergoes a complicated change in shape according to the internal evaporation volume of component 2, the strength of component 2 and the applying conditions of heat.
On the other hand, a clearance between the bottom of a package and a printed circuit board in component 2 is smaller due to the development of a thinner package and when the dimensions of the package bottom exceeds this clearance due to a transitional transformation by heat, the lead wires of component 2 ark floated; and solder is not sufficiently applied to the lead wires and it is expected that this poor soldering causes a failure.
FIG. 1B shows such a virtual inflation at the bottom of the package. In this case when a portion below the integrated circuit chip (IC) 4 in component 2 expands and protrudes downwards from the end of the lead wire even for an instant, a failure due to poor soldering occurs. However, when the package shrinks and restores within the clearance after the reflow, only poor soldering remains and its cause cannot be specified. Therefore, in the conventional method it is difficult to ascertain whether there are any problems.